1. Field of the Invention
The present invention relates to a coaxial connector used as an input/output terminal of communication equipment, and to a converter including the same for receiving satellite broadcasting.
2. Description of the Background Art
A coaxial cable is commonly used to connect communication equipment. Thus, communication equipment is provided with a coaxial connector as an input/output terminal. In a converter for receiving satellite broadcasting, for example, a coaxial connector is provided on a chassis as an output terminal to send an electric signal to a connector plug of a coaxial cable.
FIG. 10 is a cross-sectional view of a structure of a conventional coaxial connector, which is taken along an axial direction. FIG. 11 is a cross-sectional view taken along the line XI-XI shown in FIG. 10. To simplify the descriptions, a tip side of the coaxial connector, that is, the side into which the coaxial cable is inserted is referred to as a front side, and a bottom side is referred to as a rear side hereafter.
As shown in FIG. 10, a coaxial connector 1E is formed with a central contact 10, a first holding member 20, a second holding member 30, and a shell 40. Central contact 10 includes a terminal reception portion 11, a spaced portion 12, and a trunk portion 13. Central contact 10 is formed with a conductive material, and elastically holds a central terminal of a connector plug of a coaxial cable with terminal reception portion 11 located on its front end. The elastic force to hold the central terminal of the coaxial cable is provided by spaced portion 12 continuously formed in the rear of terminal reception portion 11. That is, terminal reception portion 11 is elastically energized by spacing terminal reception edges of central contact 10, as shown in the drawing. Trunk portion 13 is continuously formed in the rear of spaced portion 12, and has its rear end connected to a pattern of a circuit substrate 60 with solder 70.
First holding member 20 is formed with a cylindrical insulator including a square hole 21 in its center. Trunk portion 13 of central contact 10 is inserted and held in square hole 21. A link projection 22 is provided on a front end of first holding member 20. Link projection 22 is a site to hold spaced portion 12 of central contact 10 and to link first holding member 20 to second holding member 30. In addition, first holding member 20 has an abutting surface 25 in a plane intersecting with an axial direction. Herein, a portion of first holding member 20 which holds spaced portion 12 of central contact 10, that is, link projection 22 is referred to as a first region 20A, and a portion which holds trunk portion 13 is referred to as a second region 20B. That is, second region 20B is located in the rear of first region 20A.
Second holding member 30 is formed with a cylindrical insulator including on its front end a terminal insertion opening 31, into which the central terminal of the connector plug of the coaxial cable is inserted. Second holding member 30 is attached to link projection 22 of first holding member 20 so as to cover terminal reception portion 11 and spaced portion 12 of central contact 10. This attachment is performed only by fitting first holding member 20 into second holding member 30. In this step, second holding member 30 is positioned by abutting on abutting surface 25 of first holding member 20.
Shell 40 is formed with a substantially cylindrical conductive material which is formed to extrude forward from a prescribed site of a chassis 50, and receives and outer terminal of the connector plug of the coaxial cable. A thread 41 is provided to a prescribed position of a peripheral surface of shell 40 to maintain the connection with the connector plug. Chassis 50 is generally made of aluminum alloy, zinc alloy or the like, and shell 40 is formed by a through hole for die-casting. Therefore, a cylindrical hole of shell 40 is formed to be slightly larger in the front portion and smaller in the rear portion due to a draft angle of the casting. First and second holding members 20 and 30 linked to each other are press-fitted into the cylindrical hole inside shell 40, whereby shell 40 holds holding members 20 and 30.
In coaxial connector 1E having the above-described structure, however, because first and second holding members 20 and 30 press-fitted into shell 40 are linked only with link projection 22 provided on the front end of first holding member 20 as shown in FIGS. 10 and 11, the holding force thereof is insufficient. In addition, because shell 40 holds first and second holding members 20 and 30 only with the press-fit of an inner surface of shell 40 and outer surfaces of first and second holding members 20 and 30, the holding force thereof may be insufficient. Therefore, second and first holding members 30 and 20 may be disengaged while the connector plug of the coaxial cable is repeatedly inserted into and drawn from coaxial connector 1E.
Japanese Utility Model Registration No. 3074150 describes a coaxial connector which prevents the disengagement of the first and second holding members. FIG. 12 is a cross-sectional view of the coaxial connector taken along an axial direction, and FIG. 13 is a cross-sectional view taken along the line XIII—XIII shown in FIG. 12. As shown in FIGS. 12 and 13, in a coaxial connector 1F, a fit projective portion 24f is provided on link projection 22, which is the first region of first holding member 20, and a fit hole portion 34f, into which fit projective portion 24f is fitted, is provided in a corresponding inner surface portion of second holding member 30 in the linkage site of first and second holding members 20 and 30 in coaxial connector 1E having the above-described structure. That is, a disengagement-prevention structure is provided on a portion corresponding to first region 20A of first holding member 20. In other words, the disengagement-prevention structure is located in the front of abutting surface 25 of first holding member 20.
Therefore, the linkage between first and second holding members 20 and 30 can be kept strong by fitting fit projective portion 24f into fit hole portion 34f during the linkage of first and second holding members 20 and 30. As a result, disengagement of holding members 20 and 30 is prevented.
The holding force, however, may not be kept sufficiently even in coaxial connector 1F having the disengagement-prevention structure described above. When an ambient temperature is low, for example, as first and second holding members 20 and 30 formed with insulating members have higher degrees of shrinkage than that of shell 40 formed with a conductive member, they may be disengaged due to insertion and drawing of the connector plug.
In addition, highly complex manufacturing steps are needed to provide fit projective portion 24f on link projection 22 of first holding member 20 as in the above-mentioned structure. That is, first holding member 20 is generally produced with injection molding of plastic or the like, and a sliding core is needed for the mold in this situation, which makes the mold structure complex. Therefore, the manufacturing cost increases.